I do hope someone can help with this issue as I’m starting to pull my hair out with it.
All I get is this and it just sits there. I’ve toggled ‘Allow online access’ in the prefs.
If I try to install the legacy adding manually I get this:-
I’ve checked my PC and it seems to have given access through firewall for Blender.
Please tell me someone has had this issue and knows of the fix?
Cheers
S
Can you try: turn firewall off, install extensions, turn firewall on?
Good thinking, just tried that and still nothing! 
Whats interesting, I tried installing from local whilst offline and still got the same message.
Maybe start blender as admin - incase it is a rights problem
Have you tried to install the addon from the ‘Add-Ons’ Panel instead (not the ‘Get Extensions’)?
You can still use the old method in that panel with the addon’s zip file, and it should work in your case. 
YOU BEAUTY! That works!! Thank you so much…is there a way to not have to do that each time?
Disk on which Blender is installed (most probably C) is probably protected and doesn’t allow Blender to do some stuff unless opened as admin. You need to either remove those protections from disk or give your windows user more permissions
Unless OP has installed Blender in some weird way, or weird location on disk, there is NO reason to run Blender as admin.
To be blunt about this… NEVER EVER run a application as admin, unless it’s the only option, and then just ONLY that once.
Installing Blender will have the addons/extensions run in the same folder location as the preferences file and default skins etc.
So Blender would also not be able to even save the default scene without throwing an error.
Rights trickle down from the root to the subfolders…
It’s better to check the rights on the Blender user folders to see if there’s an issue there. It’s easy to reset rights for the user, so that should be your first option.
Again, ‘running as admin’ isn’t the solution here.
@SAuchterlonie : Nice portfolio 
edit: removed comment on installation. The screenshots show the installation directories.
